Patients with impaired hearing may be offered the implantation of a stimulating multi-channel electrode array into each cochlea (bilateral implantation), or the combination of a single cochlear implant with a hearing aid in the opposite ear (bimodal system). In both cases, through binaural stimulation the patient may experience both improved speech perception and source localization (relative to unilateral stimulation/hearing). Recent research suggests that patients using bilateral or bimodal systems will receive maximum benefit to binaural hearing if incoming sounds stimulate similar locations along the cochlea in both ears. In the case of bilateral implantation, this means that a sound should stimulate a well matched pair of electrodes (i.e., the responding electrodes in the left and right ear should each stimulate comparable cochlea regions). Research from normal hearing listeners, or electrical stimulation in animal models, suggests that auditory evoked potentials could be used to measure binaural processing. In general terms, three different types of binaural responses have been measured:    1. Binaural interaction component: (cf. e.g. [Dobie & Norton, 1980], [Riedel & Kollmeier, 2006], [Smith and Delgutte, 2008], [He, Brown, & Abbas, 2012], or [Fowler & Horn, 2012]).    2. Auditory steady-state response (cf. e.g. [Maki, Kawase, & Kobayashi, 2009] or [Ishida & Stapells, 2009]).    3. Late evoked potentials (cf. e.g. [Dajani & Picton, 2006], [Massoud et al., 2011], [Ross, Tremblay & Picton, 2007], or [Ross, 2008]).
US2006100672A1 deals with systems and methods for matching pitch information between bilateral cochlear implants in order to maximize a patient's listening experience. The system permits an electrode array of a first cochlear implant to be pitch matched to an electrode array of a second cochlear implant system by utilizing virtual electrodes, which enable cochlear stimulation at a location in between physical electrodes on the electrode array. At least one electrode of the first electrode array is mapped to a virtual electrode of the second electrode array.
US20090254149A1 describes an objective measurement of cochlear implant operation which coordinates the delivery to a patient of an acoustic signal and an electrical signal. The acoustic signal is developed as an acoustic stimulation input to the ear canal of a patient, and the electrical signal is developed as an electrical stimulation input to intracochlear electrodes of a cochlear implant. The evoked response in the patient to the delivered signals is then measured.
In the present context, a bilateral hearing assistance system is intended to comprise a hearing assistance device-pair (first and second hearing assistance devices) adapted for being worn at or in, or partially or fully implanted in the head at, left and right ears of a user, respectively. The hearing assistance device-pair may be lacking the capability of exchanging data between them. Alternatively, the hearing assistance device-pair may be adapted to be able to exchange data between them, ‘data’ being audio signals, control signals (such as the frequency allocation map), and/or other parameters (such as the relative timing between signal in each ears).